The present exemplary embodiment relates generally to compensation of banding from multiple sources in a marking platform. It finds particular application in conjunction with a multicolor marking platform with xerographic marking engines. However, it is to be appreciated that the exemplary embodiments described herein are also amenable to various other types of marking engines and other types of marking platforms.
Banding is a type of image quality defect that occurs on printed pages. It manifests itself as a variation in density with respect to the process direction. Most banding is periodic. Periodic density variations may be characterized by frequency, amplitude, and phase in relation to a fundamental frequency, as well as harmonics. Various sources of banding exist in a marking (or print) engine. The frequencies of these sources are typically known based on the mechanical design of the engine. The frequencies, for example, may be obtained from the manufacturer, third parties, or measured. To compensate for the banding defects, the amplitude and phase also need to be obtained from measurements.
Banding is a major contributor to the color stability of the print engine. For intermediate belt tandem engines, bands and streaks tend to be the number one image quality defect. Sources of banding are typically gears, pinions, and rollers in charging and development modules; jitter and wobble in the imaging modules; and photoreceptors (PRs) and their drive trains. Banding usually manifests itself as periodic density variations in halftones in the process direction. The period of these defects is related to the once around frequency of the banding source.
Recent work has identified techniques for identifying banding sources using measurements of test patterns on paper, using a multipage coherent fast Fourier transform (FFT) technique to identify the banding sources. Further, a cubic spline interpolation technique has been used to fit banding signatures to single known sources, such as PR 1x. The cubic spline interpolation technique has also been applied to derive an optimal exposure correction for single known sources across the tone reproduction curve (TRC) for banding compensation. However, multiple banding sources (e.g., PR, developer roller, bias charge roller (BCR), bias transfer roller (BTR), drive rollers, etc.) are frequently present in many current engines and profiles of these sources may change over time. Currently, no system exists to efficiently compensate for banding from multiple sources.